The conveyor belt can be provided with different auxiliary devices, such as belt steering assemblies for holding the belt in a laterally correct position, scraping devices for scraping material in powdered form, or steering arms for steering small items such as cardboard boxes.
Some conveyor belts can be used in both directions, in which case it may be necessary to alter or switch the position of the auxiliary devices depending on the belt's transport direction.
In Norwegian patent application no. 962268 there is disclosed a reversible belt steering assembly for centering conveyor belts which comprises a rotating mechanism which is rotatable about an axis perpendicular to the conveyor belt and which supports at least one steering roller for the conveyor belt, and a first transfer mechanism which supports first guide rollers. The first guide rollers are steered laterally by the conveyor belt relative to the conveyor belt's longitudinal direction, and the first transfer mechanism by means of a lateral displacement of the conveyor belt from a neutral position transfers the first guide rollers' movement to the rotating mechanism for rotating the steering rollers to a position where they steer the conveyor belt back to the neutral position. The reversible belt steering assembly also comprises other guide rollers and a second transfer mechanism which corresponds to, and is arranged opposite to the steering rollers and corresponding to the first guide rollers and the first transfer mechanism. A switch mechanism connects and disconnects the first and second transfer mechanisms relative to the rotating mechanism, depending on the belt's transport direction.
Norwegian patent application no. 962268 thus describes an auxiliary device for conveyor belts which is connected and disconnected depending on the belt's transport direction.
The switching device which is employed in the above-mentioned and other auxiliary devices may be manual or automatic. In the case of conveyor belts which form part of automated transport systems, for example for granulated ores in processing plants, the switching devices must be automatic. Such automatic switching devices can be driven by hydraulic, pneumatic or electric motors or linear actuators, for example pneumatic cylinders, which are controlled by electrical signals from a control unit which also controls the belt's propulsion motor, or electrical signals directly from the propulsion motor. This can be done in a number of different ways, all of which entail installation of electric cables, connections and other electrical devices. Such installations are expensive, and may also involve undesirable maintenance, particularly in areas which are exposed to dust, humidity, heat or cold. Thus there is a need for a switching device which is not dependent on electrical, pneumatic or hydraulic installations.